Zinc oxide semiconductor materials comprising zinc and oxygen as constituent elements have recently attracted considerable attention since they can emit not only blue light but also near ultraviolet rays of 400 nanometers or less because of their wide band gap similarly to semiconductor materials such as gallium nitride and the like. Further, their applications to photodetector, piezoelectric device, transparent conductive electrode, active device and the like have also been expected without being limited to light emitting device.
To form such a zinc oxide semiconductor material, various methods such as MBE method using ultra-high vacuum, sputtering, vacuum evaporation, sol-gel process, MO-CVD method, and the like have been conventionally examined. With respect to the light emitting device, the MBE method using ultra-high vacuum is widely used from the viewpoint of crystalline.
However, the MBE method can provide a layer having crystallinity similar to single crystal, compared with other methods, but had problems that the necessity of forming an ultra-high vacuum of extremely high level results in the increase in size and cost of a device for proving such ultra-high vacuum, and the mass productivity is too poor to realize an inexpensive light emitting device because the production in ultra-high vacuum is indispensable.
Accordingly, this invention has been attained from the point of the above-mentioned problems, and has an object to provide a method for preparing a zinc oxide semiconductor material with the high crystal quality equal to or more that by the MBE method without requiring the ultra-high vacuum as in the MBE method.